This invention relates to a facsimile receiver, and more particularly to an apparatus of the kind having a continuous helix on a printing drum.
In this type of apparatus, the printing on electrolytic paper results from the passage of current through the paper from a printing bar disposed adjacent the paper. The passage of the current is obtained by the scanning of the paper using a helical conductor supported by a rotating drum which applies the paper against the printing bar. This type of apparatus requires periodic replacement of the paper roller and the printing bar, which has the disadvantage that it involves the dismantling of a considerable part of the apparatus.
According to the present invention there is provided a facsimile receiver comprising a rotatable drum carrying a printing helix, a printing bar, a support for the printing bar, a return lever mounted on a control shaft parallel to the drum for pivoting the support from a rest position away from the drum to an operative position where the printing bar bears on the helix, a cam mounted on the drum shaft, a control lever mounted on the control shaft and pivoting with this shaft under the action of the cam, a locking finger arranged in the plane of the cam and locking the control lever when it has pivoted under the action of the cam, an electromagnet for moving the control lever from the locking position in the plane of the cam to an unlocking position outside the plane of the cam, a first spring pivoting the control lever in the opposite direction after unlocking, and a second spring returning the control lever to the plane of the cam after unlocking.
Preferably the axis of articulation of the chassis lies along the axis of the paper roller. In addition, in order to reduce the wear on the printing bar, the support for the printing bar carries a sliding part which is itself provided with a slider having one end driven by the rotation of the guide roller in a groove formed as a closed loop in its periphery.